642
FXUS65 KPIH 222151 CCA
AFDPIH

Area Forecast Discussion...CORRECTED
National Weather Service Pocatello ID
251 PM MST Fri Nov 22 2024

.SHORT TERM...Today and Saturday.
There continues to be a broad upper level low circulation off the
coast of Washington with atmospheric river moisture rotating
around this low and poised to stream into our area. Currently
there is limited moisture moving into our area, mainly the western
Central mountains.

By this evening models show moderate to heavy moisture starting
to stream into the western Central mountains and Sawtooth
mountains and then moving east by Saturday morning over our entire
area by Sunday. Snow levels are high this evening, around 7000 to
7500 feet over our western areas and 6000 to 6500 feet for our
eastern areas. Snow levels drop to the valley floors by Saturday
evening, mainly after most precipitation has come through. Expect
8 to 12 inches with up to 16 inches of snow for extreme western
peaks for the Western Central mountains and Sawtooth mountains.
Winter Storm warning are in effect for these areas. Look for 2 to
8 inches of snow for the Frank Church Wilderness, Lost river Range
and the Centennial mountains/Island park areas. Winter weather
advisories are in effect for these areas. Look for 1 to 4 inches
for other areas above around 6000 to 6500 feet. The Wasatch
mountains will likely see higher snow amounts up to 5 to 9 inches
of snow. A winter weather advisory is in effect for the Wasatch
mountains. From the NBM model there is about a 30 to 40 percent
chance of Stanley to get 3 inches of snow tonight through Saturday
and about a 5 to 15 percent chance of Ketchum to get 3 inches of
snow during the same time frame. There is a 80 to 90 percent
chance of 7 inches of snow for Galena Pass tonight through
Saturday. There is only a 15 to 25 percent chance of lower
elevations in Island Park to see 5 inches of snow, while the
mountains around Island Park, along the Montana Divide, have a 75
to 85 percent of receiving 5 inches of snow. The Wasatch mountains
also look to have a 75 to 85 chance to receive 5 inches of snow
with this system. The Snake plain will likely see a trace of snow
late Saturday afternoon to early evening when the cold air reaches
the valley floors. Expect wind gusts of 20 to 30 mph with
isolated ridge tops gusting to 40 mph Saturday afternoon. Expect
blowing and drifting snow, mainly above 6500 feet. Expect valley
rain around .05 to 0.15 mainly across the Snake River plain,
Eastern Magic Valley, and the Arco desert.

Today temperatures will be about 12 to 18 degrees above normal
with temperature in the low to mid 50s for lower elevations.
Expect above normal temperatures Saturday as well especially in
the morning and early afternoon before the cold front moves
through and drops temperatures back to near normal by Saturday
evening.
Wyatt

.LONG TERM...Sunday through next Friday.
Following a cold frontal passage on Saturday, a colder and drier
airmass will move into place for Sunday associated with a transitory
weak ridge of high pressure. Isolated snow showers will continue to
be possible especially across ERN Idaho but conditions will trend
drier for most. Our next H5 trough remains on track to move in from
the Pacific early next week which will keep temperatures at near to
below normal levels with chances for snow each day. As this trough
axis shifts overhead Tuesday into Wednesday, this is when we are
expecting to see the best coverage of scattered snow showers with
limited rain/snow mix potential across our lowest elevations below
5000 feet.

The current track and orientation of this H5 trough differs on both
the ECMWF/GFS and EPS/GEFS models with the ECMWF model favoring a
wetter solution and the GFS model a drier one. The NBM continues to
follow more closely to the ECMWF showing a first look at snow totals
in the valleys Monday through Wednesday of a T-3" with an elevation
dependent 1-6" in the mountains, locally higher south and east of
the Snake River Plain into the South Hills and ERN/SRN Highlands.
Given we are still several days out, we will continue to track the
latest evolution and track of this system to see how much moisture
is actually expected to make it into our area. Nonetheless, colder
air is expected to stick around next week with highs early in the
week in the 30s to mid 40s dropping to the mid 20s to mid 30s
starting Wednesday courtesy of NW flow filling in behind that trough
earlier in the week. For Thanksgiving, look for highs in the mid 20s
to mid 30s with a slight chance of mountain snow showers.

Looking towards late next week, EPS/GEFS models and about 80% of
ensemble clusters continue to show a Rex Block setting up across the
West with a broad ridge of high pressure over the NRN Rockies and a
H5 low building in from the Pacific to the SW CONUS. This would
bring about an extended period of cold and dry conditions in East
Idaho to finish out November into early December.
MacKay

&&

.AVIATION...18Z TAFS through 18Z Saturday.
VFR and dry conditions will continue through tonight outside of KSUN
where a mix of rain and mountain showers will be possible on station
or in the surrounding mountains this afternoon and evening. Dry
conditions will return regionwide early Saturday ahead of a cold
front building in from the west throughout the day west to east with
a mix of rain and snow, of which could be moderate to heavy at
times. First beginning at KSUN and KBYI, the front will track east
reaching KPIH, KIDA, and KDIJ later that morning into the afternoon.
MVFR/IFR CIGS/VIS will be possible associated with more organized
bands of rain and snow. As the front pushes east Saturday evening,
lingering snow showers will continue into Sunday as a colder airmass
moves in. Winds will increase with this front to around 10-20 kts
with gusts to 20-30 kts.
MacKay

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 AM Saturday to 5 PM MST Sunday
for IDZ066.

Winter Weather Advisory from 11 PM this evening to 11 PM MST
Saturday for IDZ69-071.

Winter Weather Advisory from 11 AM this Saturday to 5 PM MST
Sunday for IDZ60.

Winter Storm Warning from 11 PM this evening to 11 PM MST
Saturday for IDZ072>074.

&&

$$